tonight on "nightline," the final showdown. with only two weeks to go in a race that could not be tighter, president obama and republican challenger mitt romney squared off in florida this evening in the last presidential debate. our guides to what you need to know. she moderated the vice presidential debate. he advised george w. bush before he took the stage. martha raddatz and matt dowd tell us who they think had the upper hand in a "nightline" report card. and getting to know you. from coors light drinkers to hbo watchers, how presidential campaigns are using hyperpersonalized information about what you like to do, buy, and watch to try and win your vote. >> from the global resources of abc news, with terry moran, cynthia mcfadden and bill weir

in new york city, this is a special edition of "nightline." one on one, the final presidential debate. good evening. i'm terry moran. tonight, the highly anticipated final round as president barack obama and republican challenger mitt romney took the stage to go head to head in the last presidential debate. this is a crucial night, and it could tip the scales in a deadlocked race. a final side by side-comparison with just 15 days left now until the election. and millions of early ballots already being cast, so here's how it all happened in florida tonight. the two men who would be president squared off for the last time in the homestretch of a race that could not be any closer. this time, in boca raton, florida, swing state turf and this time sitting across from one another. you could sense the urgency of the moment. >> i thought it should have been 5,000 troops. i thought it should have been more troops.

but you know what? the answer was we got no troops through whatsoever. >> and leadership, the real issue in every presidential debate, and tonight president obama launched a direct attack on whether mitt romney is ready to be leader of the free world. >> here's one thing i've learned as commander in chief, you've got to be clear, both to our allies and our enemies, about where you stand. >> romney said obama is simply not demonstrating presidential leadership. >> attacking me is not talking about how we're going to deal with the challenges that exist in the middle east. >> neither one of these candidates ever served in the u.s. military and that hasn't happened since franklin roosevelt faced thomas e. dewey in 1944. but in this dangerous and uncertain world they tried to out-tough each other all night long. romney accused the president of undermining american strength by not spending enough on defense. >> our navy is smaller now than any time since 1917. the navy said they needed 313 ships to carry out their mission, we have under 285. >> obama brusquely dismissed him as a clueless neophyte in

national security. >> governor, we also have fewer horses and bayonets because the nature of our military has changed. the question is not a game of battleship where we're counting ships but what are our capabilities. >> romney's overall point, obama has presided over an era of american weakness that began in its first days in office on what romney calls an apology tour. >> you said that on occasion america had dictated to other nations. mr. president, america has not dictated to other nations. we have freed other nations from dictators. >> obama's response, romney is a shallow and unserious foreign policy candidate. >> if we're going to talk about trips that we've taken, when i went to israel as a candidate i didn't take donors, i didn't attend fund-raisers, i went to yad vashem. >> country after country, crisis after crisis, they slugged it out. flash point, iran, another war in the middle east.

that awful possibility looms over this election. with news breaking over the weekend that the obama administration is seeking one-on-one talks with iran to avoid war, the nuclear standoff dominated part of the debate tonight. the president offered a dramatic contrast. >> when i came into office, the world was divided. iran was resurgent. iran is at its weakest point economically, strategically, militarily than in many years. >> from the very beginning one of the challenges we've had with iran is that they have looked at this administration and felt that the administration was not as strong as it needed to be. i think they saw weakness. >> flash point, iraq, a hugely unpopular war, a strategic blunder. president obama seemed to surprise romney by arguing that he wanted to keep fighting it. >> and the challenge we have, i know you haven't been in a position to actually execute foreign policy, but every time you've offered an opinion, you've been wrong.

you said we should have gone into iraq, despite the fact that there were no weapons of mass destruction. you said that we should still have troops in iraq to this day. >> romney struggled to answer. >> with regards to iraq, you and i agreed, i believe that there should have been a status of forces agreement. oh, you didn't want a status of forces -- >> no, what i would not have done is left 10,000 troops in iraq that would tie us down and that certainly would not help us in the middle east. >> i'm sorry. you actually -- there was an effort on the part of the president to have a status of forces agreement and i conferred in that and said we should have some number of troops that stayed on. >> flash point, osama bin laden and al qaeda. 11 years after the 9/11 attacks, terrorism and how to fight it remains a crucial presidential responsibility in the 21st century. president obama rides high in the polls on this issue for one big reason. >> tonight, i can report to the american people and to the world that the united states has conducted an operation that killed osama bin laden, the

leader of al qaeda. >> tonight, the president practically boasted and slammed romney. >> when it comes to going after osama bin laden, you said, well, any president would make that call. but when you were a candidate in 2008, as i was, and i said, if i got bin laden in our sights i would take that shot, you said, we shouldn't move heaven and effort to get one man. >> mitt romney tried to undermine the president's bin laden triumph with a blunt line. >> i congratulate him on taking out osama bin laden and going after the leadership in al qaeda, but we can't kill our way out of this mess. we must have a comprehensive strategy to help reject this kind of extremism. >> at the end both men had probably achieved some of what they'd come to do, project strength, demonstrate competency and get the debate out of the way so they can refocus on domestic issues where this election will be decided. the commander in chief debate although they did debate plenty of domestic issues in there, as

well. and just ahead, she moderated the vice presidential showdown. he helped george w. bush run his campaign, martha raddatz and matt dowd tell us who they think made the grade tonight for a "nightline" report card.

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>> announcer: this special edition of "nightline," one on one, the final presidential debate continues. so let's do the "nightline" report card. i'm joined now by abc's senior foreign affairs correspondent martha raddatz who mod waited excellently the vice presidential debate. >> thank you. >> and matt dowd, our abc news consultant who was also chief strategist for george w. bush. let's get right to it and great them on the commander in chief aura they projected.

mitt romney, what do you think? >> b minus. >> b minus. >> "b." >> tough grade. >> tough grade. well, i think basically because he backed off all his peace and strength. some of the statement he said you can't kill your way out of this mess. i wondered what mitt romney was talking about from the mitt romney we used to know. >> a change in persona. >> a change in persona so maybe not the commander in chief "a" plus. >> what do you think? >> a "b." i thought he came across as someone you could see as president of the united states and so that little litmus test he could but didn't come across as strong and assertive as he did in his first debate and let the president become that more which we'll talk about in a second but i think he could be commander in chief and you could see him as president but nothing overwhe overwhelming. >> so he's running against the combh but let's grade him. how about obama do on projecting

that commander in chief authority. >> i thought air forcen "a" minus. >> "a." >> you're a tough "a." >> i haven't given an "a" to anyone in this series of debates. i thought it was his best moment and to me the commander in chief test and strong and decisive is the most important thing in the campaign. why mitt romney rose and in the aftermath of the first debate and i thought the president came across that way. there were a few instances i think he came across a little aggressive but as you watched the debate i think you could see he was clear and could make the decisions you need to make. in that regard i gave him an "a." >> he seemed more confident. >> he is the commander in chief. let's just leave it at that. it wasn't quite as hard for him to reach that level of an "a" or "a" minus as it was for mitt romney. >> why did you give him the "a" minus. >> there were a couple of things he said that weren't like on the status of forces agreement that he wasn't quite right talking about the fact that mitt romney said he wanted 20,000 troops to

remain. president obama's administration wanted troops to remain italian, as well. they just were unable to get a status of forces agreement so that's where he got -- >> they got stiffed by iraq. >> i'm a hard grader too. >> you are. so you just raised something. let's grade them on accuracy in the foreign policy debate. how accurate was what they said. mitt romney. >> "b" minus. >> "b." >> tough on mitt romney again, why? >> i just think all these things, it's the old adage accurate but not true styes. things aren't exactly right. >> what didn't you like about -- what did you find in error or slightly slippery in what romney said. >> well, i thought there were a couple of cases when he was talking about syria. when he was talking about we want to keep trying and just want to arm -- we want to arm some of the rebels but we have to figure out who they are. i just think there's so much nuance in these things. basically i hate giving these grades because -- >> i can tell. >> because there's so much

nuance in this. it's really hard to give a definitive grade. matt has no problem with that. he was grading right away. >> but especially in the foreign affairs area. >> yeah, i have no problem and saying i made a mistake a day later saying i screwed up. the interesting thing about the debate and sort of saw accuracy as substance on foreign policy in the debate i didn't see mitt romney make any distinction with the president of the united states. i thought his strategy was me too. for whatever the president just said, me too but i'll do slightly something different but i won't say what it is. he said exactly what the president said. >> okay, let's give the president a grade on accuracy. >> i'm going with a "b" minus. that's back to the status of forces agreement and just the same thing. it's just the nuance. i find myself on those foreign policy things and no one else in america is doing this but me. >> because you know it so well. >> it's those tiny things. >> your grade. >> a "b." for the same exact reason. there was no real debate on foreign policy. >> no solutions, nothing like

that. who needs solutions, right? >> not that you thought it would change next year. >> did you didn't watch it, you didn't miss anything. who is the winner in your judgment? >> i'm not going to say there's a fair winner but i would say overall obama probably scored more points because he goes into this as commander in chief so he walks out there does the job he's done. mitt romney probably was just showing up and saying, look, i'm on the same stage as he is. i don't want to make any waves. i don't want to talk about war or scare anybody. >> because of barack obama got the commander in chief passing colors i think he won and i think it was fairly clear and fairly decisive. i don't think mitt romney hurt himself but i think barack obama may have helped himself a point or two in the course of the debate by winning this tonight. >> romney may have been playing it too safe. >> a little too soft in this. he became the peace candidate in the course of this debate. >> matt, martha, thanks very much. that's a "nightline" report card. next up from your beer of choice to what show you watch before bed. how presidential candidates are

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do you cub scribe to hbo? >> what kind of beer do you drink? >> inquiring minds including the presidential campaigns want to know because of something called micro targeting. this is the new frontier in personalized campaigning. it works by finding often baffling correlations between the stuff you like and who you're likely to vote for. here's abc's john donvan. >> are you ready to go? >> as this tight election heads towards a photo finish in 15 days there are two presidential campaigns taking place. there's the one you saw tonight on the debate stage. it's also there in the tv ads

and the big speeches. but then there is the other campaign, a stealthier one where messages get tailored just for you and are delivered not in front of the tv cameras but right to your mailbox. >> they'll have a prediction of the likelihood you're a gun owner so the campaign with can make sure when they're talking about gun rights they're sending it to someone who likely owns a gun. >> their neighbor will get something else, get something not at all. >> reporter: called microtargeting sass sasha eisenberg brighter of "the victory lap." >> you can have a different conversation with theoretically everyone on the block. >> reporter: they have to figure out what's important to you. how? data. truckloads of it. in the modern world you are leaving trails of information about yourself everywhere you go and the campaigns are buying it up. they use it to build a profile of you. say you watch "30 rock" and drink molson. that means you're probably a democrat that votes frequently. coors light and watching "ncis,"

odds are you are a loyal republican. >> how much is it about changing people's mines versus trying to get people who would vote for you go vote on election day? >> this is the big change in way campaigns think in the last decade. it's far less about changing people's minds and far more about modifying their behavior. >> reporter: guess what, there's's an app for that as sasha showed me. they want to knock on the doors and get out the vote, not just any doors. >> all the data they have and micro targeting algorithms and who they want to interact with. these flags represent each particular house. >> reporter: who in this neighborhood is most likely to vote for their guy. this is a real map of this street we're on. >> yes. >> reporter: these flags represent real houses? >> real houses. >> reporter: like, for instance, whoever lives at this house which we're blurring a bit for privacy, the app knows stuff about this person. what do we know.

>> there's a 73-year-old woman, a registered democrat, her name begins with "j." her last name begins with an "r." >> reporter: if there's a knock on the door and an obama or romney volunteer, though know something about you. >> they know a lot about you and they've made a whole lot of assumptions about you. >> reporter: they're not at your door by accident. >> no, we're way past accidents. >> reporter: which means campaign ads are copping up in the unlikeliest places. >> another variable that is helping to predict support, the presence of a teenager in the household and found video games where you can buy ads and boat early vote reminders. >> reporter: there's no such thing as too narrow a niche. in a mailer to homes in northern virginia where there is lyme disease concern, romney said he's against it. there's nothing to show definitely these tactics put them over the finish line, instead eisenberg says in the end the single most important piece of predictive data isn't

what beer you drink but whether you're a registered democrat or republican which is publicly available on the voter roll. all the rest is extra but it's a lot. sos like they have the whole neighborhood and can see into the political soul of people who even now sitting this their houses. >> right. >> reporter: does that seem just a little creepy? >> the campaigns, even though they have the tools to convey specific messages, the costs of doing it are high. >> reporter: in other words, when they knock on your door -- >> we're out here knocking on doors. >> reporter: -- just because they found you doesn't mean you have to answer. john donvan, abc news, washington. >> big brothers are watching you. thanks to john donvan, for that thank you for watching abc news. we hope you check in for "good morning america." we're always online at abcnews.com. "jimmy kimmel" is coming up next. we'll see you here tomorrow.